Deep submergence vessels of interconnected radial-filament spheres

ABSTRACT

A class of hollow, shell-type, deep submergence vessels with low weight to displacement ratio and high resistance to external hydrostatic pressures and made of interconnected shells in the form of equatorial segments of unidirectional radial fiberreinforced resin spheres is disclosed. Suitable stiffening rings are provided to interconnect and take up stresses at the junctures of the sphere sections of such a vessel. The foregoing abstract is not to be taken either as a complete exposition or as a limitation of the present invention, and in order to understand the full nature and extent of the technical disclosure of this application, reference must be had to the following detailed description and the accompanying drawings as well as to the claims.

United States Patent 3 lnventors Appl. No. Filed Patented Assignee DEEP SUBMERGENCE VESSELS OF INTERCONNECTED RADIAL-FILAMENT SPHERES 16 Claims, 16 Drawing Figs.

[52] US. Cl 220/5 A, 220/3, 220/83 [51] Int. Cl. B65d 1/16, B65d 1/40 [50] Field of Search 220/3, 5 A, 83,18,9 F, 5; 114/16 [56] References Cited UNlTED STATES PATENTS 2,920,784 1/ 1960 Boardman 220/1 B 2,973,783 3/1961 Boe 220/83 UX 3,490,638 1/1970 Elliott et al. 220/5 A FOREIGN PATENTS 680,819 2/1964 Canada 220/83 332,861 12/1935 Italy 220/3 Primary Examiner--Raphael H. Schwartz Attorney-Norbert P. Holler ABSTRACT: A class of hollow, shell-type, deep submergence vessels with low weight to displacement ratio and high resistance to external hydrostatic pressures and made of interconnected shells in the form of equatorial segments of unidirectional radial fiber-reinforced resin spheres is disclosed. Suitable stiffening rings are provided to interconnect and take up stresses at the junctures of the sphere sections of such a vessel.

The foregoing abstract is not to be taken either as a complete exposition or as a limitation of the present invention, and in order to understand the full nature and extent of the technical disclosure of this application, reference must be had to the following detailed description and the accompanying drawings as well as to the claims.

DEEP SUBMERGENCE VESSELS OF INTERCONNECTED RADIAL-FILAMENT SPHERES This invention relates to deep submergence vessels for use in underwater research and exploration, antisubmarine warfare, and the like.

Hollow vessels capable of withstanding extremely high external pressures are in great demand for oceanographic and various other types of both civilian and military activities, including underwater research and exploration, antisubmarine warfare, etc., to serve as the load-carrying envelopes for underwater structures, as vehicles for men and/or instruments, and as buoyant elements for attachment to underwater vessels. It is well known that metal shells can be constructed to provide the strength and resistance to buckling which vessels need to withstand the tremendous compressive stresses to which they are subjected at extreme ocean depths. Such metallic vessels are severely limited in effectiveness, however, by their high weight-to-displacement ratios; at wall thicknesses sufficient to meet the strength and elastic stability requirements, vessel weight becomes excessive. Supplementary buoyancy means must be provided, therefore, increasing the bulk and decreasing the maneuverability of the vessel.

One class of structures which we have devised to overcome these disadvantages is the unitary-shell type of fiberreinforced resin or radial-filament sphere construction of the deep submergence vessels disclosed in our copending application Ser. No. 522,675 filed Jan. 24, I966, now US. Pat. No. 3,490,638 issued Jan. 20, 1970, the entire disclosure of which is hereby incorporated in the instant application by reference. For a number of uses and situations, however, it may be desired to elongate and increase the internal capacity of such a deep submergence vessel while retaining the advantageous strength characteristics of the spheres without being limited to the creation of bigger spheres and the task of coping with an intolerable increase of hydrodynamic drag.

It is an important object of the present invention, therefore, to provide hollow, shell-type, multisection, deep submergence vessels capable of withstanding high external pressures and possessed of relatively high ratios of compressive strength to weight and of elastic stability to weight, and a relatively low ratio of weight to displacement for a given depth capability.

It is another object of the present invention to provide such vessels made of hollow filament-reinforced resin sphere sections in which all the fibers are oriented substantially normal to the surfaces of the sphere sections.

Generally speaking, the objectives of the present invention are attained by the use of two or more axially aligned and interconnected shell sections in the form of equatorial segments of radial-filament spheres. The term equatorial segment is here used to designate a section of a sphere extending through an arc of less than 90 to at least one side of a diametral or equatorial plane of the sphere. The various segments are connected to one another by means of preferably fiber-reinforced resin stiffening rings to which they are appropriately secured and which also serve to support the stresses at the junetures of the connected segments. The end members of each series of shell segments are closed off at their distal regions, preferably by means of domelike or polar sphere segments of the required dimensions and curvature to complete the spherical surfaces of the end sections of the vessel.

The foregoing and other objects, characteristics and advantages of the present invention will be more clearly understood from the following detailed description of several embodiments thereof when read in conjunction with the accompanying drawings, in which:

FIG. 1 is a perspective illustration of a multisection quasicylindrical vessel constructed of a plurality of interconnected radial-filament spheres in accordance with the present invention;

FIG. 2 is a fragmentary axial section, on a greatly enlarged scale, through the vessel shown in FIG. 1;

FIG. 3 is a perspective view of a large block of unidirectional filament-reinforced resin which can be employed as the basic starting material for one particular method of construction of radial-filament spheres to be used in the making of vessels in accordance with the present invention;

FIGS. 3a and 3b are similar views illustrating, respectively, severed parts of the block of FIG. 3 and their reassembly into a relatively thin unidirectional slab;

FIG. 4 is a fragmentary perspective illustration of the slab of FIG. 3b as cut transversely in the first step of the illustrated sphere-constructing method;

FIG. 5 is a perspective illustration of a built-up intermediate structural member made from the cut slab shown in FIG. 4;

FIGS. 6, 6a, and 6b are side elevational, top plan and end elevational views, respectively, of further intermediate structural members cut from the member shown in FIG. 5;

FIGS. 7 and 7a are perspective illustrations, respectively, of parts of a sphere built up from a multiplicity of the members shown in FIGS. 6 to 6b by further steps of this method; and

FIGS. 8 to 11 are plan views of other vessel configurations which may be provided by implementation of the principles of the present invention.

To summarize briefly the basic theory underlying the radialfilament sphere concept, it was pointed out in our aforesaid copending application that, when a three-dimensional structure composed of a cured thermoset resin matrix having embedded therein a multiplicity of parallel unidirectional, highmodulus filaments is subjected to balanced bidirectional compressive stresses normal to each other and to the filament orientation, the filaments are additionally stressed in tension by shear stresses coupled from the resin matrix. Also, in a hollow spherical vessel subjected to external hydrostatic pressure over its entire surface, the external pressure is opposed by balanced circumferential stresses in the wall of the vessel, and any given element of such a body can thus be considered as being subjected to two perpendicular compressive stresses, both essentially parallel to the vessel surface. Accordingly, if each such element of the shell body is composed of a unidirectional filament slab in which all the individual fibers are oriented substantially radially of the sphere and thus normal to the plane of application of the circumferential compressive stresses, the fibers in each element of the shell body support the stresses in lateral compression and are also stressed longitudinally in tension by resin shear. Thus, no buckling of the filaments can occur, and the tension in the latter restrains the resin from flowing therealong and obviates the requirement of a high degree of straightness in the fibers and effective lateral support thereof by the resin. This is precisely opposite to the situation existing in conventional filament-wound spheres, where transverse buckling of the filament windings is resisted only by the lateral support provided by the resin.

It was also pointed out in our said application that deep submergence vessels are also generally characterized by a figure of merit which is expressed as the weight-to-displacement ratio (W/D), a factor which for a given value of critical pressure, i.e. depth capability, for an elastic stability-limited vessel is related to the properties of the material of which the vessel is made, being directly proportional to the density and inversely proportional to the square root of the modulus of elasticity, i.e. the compressive strength, of the wall material. A low value for the ratio W/D represents a large payload capability for the vessel, and for a sphere of a given size and intended for a specified critical pressure, better performance (lower W/D) results from a higher modulus or compressive strength and a lower density. Accordingly, effective implementation of the radial-filament sphere concept entails the use of unidirectional fiber and resin building elements characterized by an optimally low value of the ratio of the density of the composite material to the square root of the transverse modulus of the element (i.e. the modulus perpendicular to the filament direction). Since this ratio decreases as the modulus increases, it is preferred to employ both resin and filer components of high modulus, inasmuch as both contribute to the transverse modulus of the composite element, but such other factors as permissible density, weight, etc., may place limitations on the choice of resin and/or fiber for the elements.

In any event, the effectiveness of such spheres in sustaining extremely high external pressures stems directly from the radial orientation of the filaments which provides, under conditions of balanced biaxial stress, strength and elastic stability far beyond those of conventional filament-wound constructions. Stated in other words, the radial-filament construction is circumferentially isotropic, i.e. it is equally effective in all circumferential directions, whereas in conventional filamentwound structures a given filament provides support primarily in a single direction, which makes it approximately only half as effective as a radial-filament construction.

Merely by way of example, in actual practice we found that excellent results are achieved by using glass filaments (having a modulus in the range of about to 1% million p.s.i.) as the fiber component in a resin matrix composed of an epoxy system having a modulus of about 430,000 p.s.i. Alternatively, the fiber component of the building elements may include asbestos fibers (modulus in the range of about 24 million to 25 million p.s.i.), boron filaments (modulus in the range of about 50 million to 60 million p.s.i.), carbon filaments (modulus in the range of about 20 million to 70 million p.s.i.), sapphire whiskers, tungsten whiskers, etc. The resin component likewise may be composed of other epoxy resin systems having different modulus values, as well as of various other resins characterized by relatively low values of the density-modulus ratio, including such as phenolics, melamines, and the maleic alkyd/styrene copolymer types of polyester resins.

Referring now to the drawings in greater detail, FIGS. I and 2 show a multisection, elongated, hollow shell-type quasicylindrical vessel I0 made of a plurality of radial-filament sphere segments 11, I2, 13 and 14 each built up in accordance with certain principles of construction to be more fully explained presently, the shell wall being composed of unidirectional fiber-reinforced thermoset resin, and the individual short filament lengths 15 extending from the inner to the outer surface of each shell section and substantially normal to both said surfaces and constituting above about 65 percent, preferably between about 75 and 90 percent, of the total volume of the wall. Each of the various segments constituting the sections of the vessel 10 is an equatorial segment of a sphere, i.e. a segment having two coaxial openings and preferably subtending an angle A extending to both sides of the equatorial plane of the sphere and of a magnitude determined by design requirements. The distal openings of the two outermost end sections 11 and 14 of the vessel are shown as being closed off by respective domelike or polar sphere segments or end caps 16 and 17 of the same curvature as the associated equatorial segments and of the appropriate arcuate dimensions to fit smoothly into said openings so as to define continuous spherical surfaces therewith. The central angle A of each shell section of the vessel 10 may be symmetrical, i.e. the portions of any given equatorial segment to either side of the equatorial plane thereof may subtend equal angles as illustrated merely by way of example for the segment 12 at aa, but if desired or dictated by design requirements, the angle A may be asymmetrical, i.e. the respective portions of any given equatorial segment on opposite sides of the equatorial plane may subtend unequal angles as illustrated by way of example for the segment 11 at a-a.

The various adjoining equatorial sphere segments are interconnected by means of suitable stiffening rings 18 preferably made of fiber-reinforced resin (although metal or other materials may be used if design considerations permit) having the requisite strength and modulus. Preferably, the joining of the sphere segments to the stiffening rings is effected by means of an appropriate adhesive, e.g. an epoxy resin, or by mechanical clamping in combination with a suitable seal (not shown). The rings 18 are constructed with beveled outer faces 18a designed to mate with the boundary surfaces of the sphere segments to be interconnected thereby and so as to have each beveled face oriented radially of the abutting sphere segment.

No stiffening rings are required, of course, at the junctures between the distal end openings (if any) in the end shell sections 11 and 14 and the associated end caps I6 and 17.

The construction of radial-filament sphere segments suitable for assembly into multisection quasi-cylindrical vessels 10 according to the present invention may be effected in any of the ways of building radial-filament spheres disclosed in our aforesaid copending application. The preferred building method, however, is the one which in said application is designated the barrel method. In the implementation of this method, restated herein in full for the sake of clarity, the starting material is a block 19 of unidirectional filament-reinforced resin (FIG. 3), of appropriate transverse dimensions, in which the filaments 19a run lengthwise of the block. The block is cut in planes transverse to the filament direction, as indicated by the lines 20, into a plurality of relatively thin strips 21 which are then laid on their sides (FIG. 3a assembled in side-byside relation (FIG. 3b), and cemented to one another at their abutting edges 21a to form a thin panel 22. It will be understood that the thickness of each of the strips 21 cut from the block 19 will be equal to the desired wall thickness of the ultimate spherical shell body.

The flat panel 22, having all filaments oriented normal to its broad faces, is then severed along oblique planes, as indicated by the lines 23 (FIG. 4), to provide a plurality of relatively narrow strips 24 of essentially trapezoidal cross section. These strips are then separated, alternate ones are inverted, and all are reassembled and cemented along their abutting faces 24a (FIG. 5), resulting in the formation of a sector 25 of a right circular cylinder (FIG. 5). Merely by way of example, for the illustrated member 25 enough stripe 24 are employed to form a sector, but quite obviously sectors of greater or smaller arc may be built up as well. (It should be understood that the elements 24 are drawn to a greatly enlarged scale in FIGS. 4 and 5 and that actually many more than five strips will be required to make up such a sector 25). The cylindrically curved sector 25, having the individual fiber lengths extending perpendicularly to the inner and outer surfaces of the sector, is then severed into a plurality of somewhat lune-shaped strips 26 (FIGS 6, 6a and 6b by making suitable paired oblique planar cuts through the sector 25 in the circumferential direction thereof, as indicated by the broken lines 2727a in FIG. 5, the paired planes of cutting being so oriented as to intersect at the axis of curvature of the sector 25.

A sufficient number of such strips 26 is then reassembled and cemented to each other in side-by-side relation (after the removal of the waste material resulting from the cutting operation) to form a barrellike body 28 (FIG. 7) having the shape of an equatorial segment of a sphere with two coaxial openings 28a bounded by annular edge surfaces 28b each of which is a zone of a cone having its apex at the center of the sphere. It will be clear, of course, that the body 28 may be formed by first building up a plurality of intermediate members in the shape of spherical sectors (not shown) from the strips 26 and then assembling such sectors into the final configuration shown in FIG. 7. Naturally, where the initial formation is of a 90 cylindrical sector 25, the body 28 extends 45 to either side of the equator of the sphere, but as previously mentioned this can obviously be varied, as desired, by a suitable choice of the are of the sectors 25.

As can readily be seen, each such barrellike body 28 constitutes a structure which can be used as a component member of a multisection vessel (i.e. one having two or more sections) such as the vessel 10 illustrated in FIGS. 1 and 2. In the case of an underwater vessel, of course, the outermost end sections thereof would have to be sealed tight, and for this purpose any such barrellike body or a lesser part thereof, e.g. a spherical sector of sufficient areal size, may be assembled and cured in the same manner as heretofore outlined to provide two blanks from which two complementary polar caps 29 (only one is shown in FIG. 7a) having boundary edge surfaces 29a mated in size and orientation to the end edge surfaces 28b of the body 28 can be derived, e.g. machined. These caps are then cemented to the respective end sections to complete the spherical surfaces thereof, as indicated at 16 and 17 in FIGS, 1 and 2. In this connection it will be understood, however, that although the interior sections of the vessel must be necessity be defined by equatorial sphere segments open at both poles, the end sections of the vessel need only one opening, and thus an equatorial segment designed to constitute an end section may actually be constructed with a central angle that is 90 to one side of the equator and a predetermined amount less than that to the other side of the equator. This, of course, would eliminate the need for a subsequent addition of an end cap.

Alternatively, the body 28 may be built up in other ways, as by initial construction of a sphere, hemisphere or spherically curved sectors in any of the ways set forth in our aforesaid application and the subsequent transformation of such elements by appropriate trimming, cutting, grinding and/or assembly operations to the form shown in FIG. 7 with either both ends or only one end open.

The principles of the present invention may, of course, be embodied in vessels differing somewhat in configuration from the quasi-cylindrical vessel 10 shown in FIGS. 1 and 2. Thus, by the use of equatorial sphere segments of suitably varying sizes, a vessel 30 (FIG. 8) with a configuration resembling that of a prolate spheroid can be constructed. A vessel 31 (FIG. 9) of a branched configuration can be obtained by combining two essentially quasi-cylindrical vessels 32 with one or more medial bridging equatorial sphere segments 33, for which purpose selected intermediate sections 32a of the vessels 32 would be provided with respective additional lateral openings 32b oriented other than parallel to the planes of the polar openings 320 of those sections. The construction of a T- shaped vessel rather than the illustrated H-shaped one would merely require omission of one of the vessels 32. A vessel 34 (FIG. 10) of polygonal closed loop configuration, e.g. square or rectangular, can be constructed by similarly combining two essentially quasi-cylindrical vessels 35 with two single or multiple lateral bridging equatorial sphere segments 36. It will be readily seen that upon omission of one of these bridging segment arrangements 36, the structure will be an open loop essentially U- or horseshoe-shaped configuration. Quite obviously, still other structural arrangements, including other open or closed curved, polygonal and branched configurations, may be designed by suitably selecting the angular relationships between the respective openings in the various sphere segments, the positions of the bridging segments, the sizes of the various segments and openings, etc. Merely by way of example, a relatively small sphere segment 37 (FIG. 11) may be connected to a considerably larger sphere segment 38, e.g. at one end of a submarinelike vessel, to serve as a sonar dome or the like. Smaller sphere segments, as will be understood, may, of course, be made with wall thicknesses proportionately less than those of larger segments designed for the same pressure capabilities.

The vessels herein described will basically he possessed of all the advantages of the radial-filament sphere construction, including not only the higher payload capability and the ability to withstand extremely high external hydrostatic pressures, but also such others as ofi'ering (a) the possibility of providing port openings and hatches by cutting a piece of suitable size directly out of the shell wall without introducing any filament end-loading stresses and without any need to provide means for preventing failure of the structure by spreading or delamination of the wall; (b) the possibility of easy repair, in the event a portion of a radial-filament sphere segment is damaged, by simply cutting out the damaged portion with a radial cut and replacing the removed shell portion with an identical mating radial-filament section which can be ccmented in place to repair the shell without loss of strength; and (c) the elimination of any need to provide the vessel with metal polar end fittings or caps to provide access to its interi- It is to be understood that the foregoing description is for purposes of illustration only, and that the structural features and relationships disclosed herein are merely representative and are susceptible to various changes and modifications none of which entails a departure from the spirit and scope of the present invention as defined in the hereto appended claims.

Having thus described our invention, what we claim and desire to protect by Letters Patent is:

l. A deep submergence vessel, comprising a hollow, shelltype body capable of withstanding high external hydrostatic pressure and made of a plurality of interconnected shell sections each constituted by an equatorial segment of a sphere, the wall of each of said shell sections being made of resin reinforced by short-length filaments which extend substantially normal to the inner and outer wall surfaces in that section.

2. A shell-type body according to claim I, said shell sections being arranged in a quasi-cylindrical configuration.

3. A shell-type body according to claim 1, said shell sections being arranged in a prolate spherelike configuration.

4. A shell-type body according to claim 1, said shell sections being arranged in a branched configuration.

5. A shell-type body according to claim 1, said shell sections being arranged in a curved configuration.

6. A shell-type body according to claim I, said shell sections being arranged in a closed-loop configuration.

7. A shell-type body according to claim 1, said shell sections being arranged in an open-loop configuration.

8. A shell-type body according to claim 1, said shell sections being constituted by sphere segments of the same diameter.

9. A shell-type body according to claim I, at least one of said shell sections being constituted by a sphere segment of a diameter different from the diameter of the next adjacent sphere segment.

10. A deep submergence vessel, comprising a hollow, shelltype body capable of withstanding high external hydrostatic pressure and made of a plurality of interconnected shell sections each constituted by an equatorial segment of a sphere having an opening in at least one region of the wall thereof where it is intended to adjoin an adjacent shell section, the wall of each of said shell sections being made of resin reinforced by short length filaments which extend substantially normal to the inner and outer wall surfaces in that section.

11. A shell-type body according to claim 10, further comprising a respective stiffening ring interposed between and secured to the proximate wall edges bounding the associated openings of each adjoining pair of said shell sections, thereby to interconnect said shell sections and serve as means for supporting stresses generated in the same.

12. A shell-type body according to claim 10, each of said openings in each of said equatorial sphere segments being disposed in a plane parallel to the equatorial plane of that segment.

13. A shell-type body according to claim 10, at least one of said openings in at least one of said equatorial sphere segments being disposed in a plane which is not parallel to the equatorial plane of that segment.

14. A shell-type body according to claim 10, at least one of said openings in at least one of said equatorial sphere segments being disposed in a plane perpendicular to the equatorial plane of that segment.

15. A shell-type body according to claim 10, wherein at least one of said equatorial sphere segments that is intended to constitute an end section of said body is a complete hemisphere to the side of the equatorial plane thereof opposite that on which said opening and the thereto adjoining shell section are located.

16. A shell-type body according to claim 10, wherein at least one of said equatorial sphere segments that is intended to constitute an end section of said body has two openings on opposite sides of the equatorial plane thereof, and a polar domelike sphere segment having the same curvature and wall structure as the equatorial sphere segment is secured to that one of said openings of the latter which is on the side of saii equatorial plane opposite that on which the other of said openings and the thereto adjoining shell section are located. 

2. A shell-type body according to claim 1, said shell sections being arranged in a quasi-cylindrical configuration.
 3. A shell-type body according to claim 1, said shell sections being arranged in a prolate spherelike configuration.
 4. A shell-type body according to claim 1, said shell sections being arranged in a branched configuration.
 5. A shell-type body according to claim 1, said shell sections being arranged in a curved configuration.
 6. A shell-type body according to claim 1, said shell sections being arranged in a closed-loop configuration.
 7. A shell-type body according to claim 1, said shell sections being arranged in an open-loop configuration.
 8. A shell-type body according to claim 1, said shell sections being constituted by sphere segments of the same diameter.
 9. A shell-type body according to claim 1, at least one of said shell sections being constituted by a sphere segment of a diameter different from the diameter of the next adjacent sphere segment.
 10. A deep submergence vessel, comprising a hollow, shell-type body capable of withstanding high external hydrostatic pressure and made of a plurality of interconnected shell sections each constituted by an equatorial segment of a sphere having an opening in at least one region of the wall thereof where it is intended to adjoin an adjacent shell section, the wall of each of said shell sections being made of resin reinforced by short length filaments which extend substantially normal to the inner and outer wall surfaces in that section.
 11. A shell-type body according to claim 10, further comprising a respective stiffening ring interposed between and secured to the proximate wall edges bounding the associated openings of each adjoining pair of said shell sections, thereby to interconnect said shell sections and serve as means for supporting stresses generated in the same.
 12. A shell-type body according to claim 10, each of said openings in each of said equatorial sphere segments being disposed in a plane parallel to the equatorial plane of that segment.
 13. A shell-type body according to claim 10, at least one of said openings in at least one of said equatorial sphere segments being disposed in a plane which is not parallel to the equatorial plane of that segment.
 14. A shell-type body according to claim 10, at least one of said openings in at least one of said equatorial sphere segments being disposed in a plane perpendicular to the equatorial plane of that segment.
 15. A shell-type body according to claim 10, wherein at least one of said equatorial sphere segments that is intended to constitute an end section of said body is a complete hemisphere to the side of the equatorial plane thereof opposite that on which said opening and the thereto adjoining shell section are located.
 16. A shell-type body according to claim 10, wherein at least one of said equatorial sphere segments that is intended to constitute an end section of said body has two openings on opposite sides of the equatorial plane thereof, and a polar domelike sphere segment having the same curvature and wall structure as the equatorial sphere segment is secured to that one of said openings of the latter which is on the side of said equatorial plane opposite that on which the other of said openings and the thereto adjoining shell section are located. 